Knife grinder

ABSTRACT

A knife grinder for chipping knives having plane beveled surfaces interconnected by a curved beveled corner surface. The knives are mounted on a rotatable head that carries them past a movable grinding unit. A powered grinding surface engages each knife while moving in an arcuate path about the corner axis of the knife along the line of engagement and while moving in arcuate paths about pivot axes perpendicular to the straight knife edges. The grinding unit is guided by a pivot frame and powered by a constantly turning crank. Automatic advancement of the grinding unit toward the knives is provided by a pawl and ratchet wheel engaged at the completion of each complete pass of the unit across the knife surfaces.

[ lFeh. $2, 1%72 [54] KNlllFE GRINDER [72] inventor: George M. Standal,1916 San Fernando Place, Victoria, British Columbia, Canada [22] Filed:Sept. 21, 1970 [21] Appl.No.: 74,093

Standal ..5 1/55 Primary Examiner-William R. Armstrong Att0rney-Wells,St. John & Roberts [57] ABSTRACT A knife grinder for chipping kniveshaving plane beveled surfaces interconnected by a curved beveled comersurface. The knives are mounted on a rotatable head that carries thempast a movable grinding unit. A powered grinding surface engages eachknife while moving in an arcuate path about the corner axis of the knifealong the line of engagement and while mov ing in arcuate paths aboutpivot axes perpendicular to the straight knife edges. The grinding unitis guided by a pivot frame and powered by a constantly turning crank.Automatic advancement of the grinding unit toward the knives is providedby a pawl and ratchet wheel engaged at the completion of each completepass of the unit across the knife surfaces.

41 (Ilaims, 11 Drawing Figures PATENTEUFEB 22 1912 SHEET 3 [1F 5 FIG. 5.

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66 INVENTOR. (EORCE M. QFTANDAL K.) 62 131 7 mm i 122%,

KNIFE canvass BACKGROUND OF THE INVENTION This disclosure relates to achipper knife grinder. An example of the type of knife involved hereinis shown in my U.S. Pat. No. 3,282,312, granted Nov. 1, 1966, titledChipper linife and Apparatus." Each knife includes a continuous cuttingedge formed by beveled surfaces joined by a curved beveled surfaceforming a comer radius.

A prior chipper knife grinder for a different form of knife is shown inmy U.S. Pat. No. 2,976,649, granted Mar. 28, 1961, entitled ChipperKnife Grinder." That disclosure is concerned with the grinding of achipper knife which requires one ground face to be in a plane and theother ground face to be curved. In that arrangement both faces wereground simultaneously by two separate grinding units.

The present apparatus is an improvement upon my earlier grinder in thata single-grinding unit is used to work upon both plane and curvedbeveled surfaces to form the required cutting edges on a set of chipperknives. This eliminates the necessity for maintaining more than onegrinding wheel surface and minimizes the mechanical complications ofoperating two grinders simultaneously. It also insures even grindingcontact across the entire knife, since the same grinding surface is usedon all surfaces.

SUMMARY OF THE INVENTION The invention disclosed herein basicallycomprises a supporting framework that rotatably carries a knife-mountinghead for releasably fixing each knife radially outward from a rotationalaxis with the knife beveled surfaces exposed and facing outwardly. Amotor is connected to the head for rotating it and the knives about theaxis to thereby move the knife surfaces about a circular path. Aknife-grinding unit is located tangential to the circular path of theknives for engaging the beveled surfaces. The knife-grinding unitincludes a grinding surface pivotally mounted about a fixed axiscoincident with the knife corner axis at the line of grinding engagementand further includes means for selectively arresting such pivotal motionand moving the grinding surface along the respective straight beveledsurfaces. A common drive element controls the knife-grinding unit tosuccessively grind the plane beveled surfaces and the intermediatecurved beveled surface of each knife.

One object of this invention is to reduce the complexity required inprior knife-grinding machines by utilizing a singleknife grinding unitto engage both plane and curved beveled surfaces along knife-cuttingedges.

Another object of the invention is to provide a knife-grinding apparatuswhich is adaptable to various sizes and shapes of knives.

Another object of the invention is to provide such an apparatus withautomatic control of grinding depth, such control being constant acrossthe entire knife. These and further objects and advantages of theinvention will appear from the following description and accompanyingdrawings which illustrate a preferred form of the apparatus.

DESCRIPTION OF THE DRAWINGS FIG. l is a front elevation view of theapparatus;

FIG. 2 is a fragmentary horizontal sectional view taken along line 22 inFIG. 1;

FIG. 3 is a top view of the apparatus as illustrated in FIG. ll;

FIG. A is a fragmentary top view of the apparatus showing the grindingunit at its opposite extreme position;

FIG. 5 is a side elevation view of the apparatus taken from the left inFIG. ll;

FIG. 6 is a view similar to FIG. 2, showing the grinding unit at itsopposite extreme position;

FIG. 7 is a side elevation view of the apparatus taken from the right inFIG. 3;

FIG. 8 is a schematic view illustrating the manner by which the knifesurfaces are engaged by the grinding wheel;

FIG. 9 is a fragmentary enlarged side elevation view similar to FIG. 7,showing the manner by which the grinding unit pedestal is angularlytilted for grinding the knife plane beveled surfaces;

FIG. MI is an enlarged fragmentary sectional view through the grindingunit as seen along line lltl-lllll in FIG. l; and

FIG. Jill is a sectional view of the grinding unit as seen along linelll-ll in FIG. Ml.

DESCRIPTION OF THE PREFERRED EMBODIMENT The grinding apparatus ismounted on a stationary reference framework 10. The knives are clampedto a knifemounting device in the form of a cylindrical head llllsupported on framework by means of a drive shaft 112 and bearings 13.The center of head If is coaxial with the horizon tal rotational axis ofshaft 12. Shaft 12 and head II are rotated about the axis of shaft 12 bya motor I5 and speed reducer l6 drivingly connected to shaft 12 by aconventional drive chain The chipping knife and an example of anapparatus in which it is employed are described in detail in my U.S.Pat. No. 3,282,312. Each knife 20 consists of a rectangular side cuttingblade 21 to which is joined a rectangular face cutting blade 22. Theblades 21 and 22 are joined along abutting edges and define an includedobtuse angle, shown as l35 in the illustrated example. A common edgeextending across both blades 21, 22 is beveled along the outer knifesurfaces, the bevel angle illustrated being approximately 34. The cornerjoining blades 21, 22 is beveled about a corner axis that lies betweenthe blades 21, 22. Referring to FIG. 8, which schematically illustratesthe grinding operation, the plane beveled surface along the side cuttingblade 21 is designated at 2A, the plane beveled surface along the facecutting blade 22 is designated at 25, and the connecting curved beveledsurface is designated at 26. The corner axis of curved beveled surfaceas is indicated at 27.

The head lll carries a plurality of mounting blocks l7 that clamp theindividual knives 20. A spring-loaded clamp 18 holds each knife 20 on anindividual mounting block 17. Any desired number of knives 20 may bemounted on head llll, which is preferably designed to hold one or twocomplete sets of knives for a chipping apparatus. The block 117 may bearranged to hold a plurality of knives facing in opposite directions ora plurality of knives all facing in a common direction about theperiphery of head Ill, depending upon the requirements of the particularchipping apparatus. For purposes of illustration, only a single-knifeblock I7 is illustrated in the overall assembly views (FIGS. l, 3, 41, 5and 7) but it is to be understood that identical blocks 17 are arrangedabout the complete periphery of head Ill and are angularly spaced so asto balance the weight of the assembly about the axis of shaft 112.

The knives 2.0 are arranged about the periphery of head If in a circularpattern with the beveled surfaces 2A, 25 and 26 facing outwardly in acommon radial orientation. In the example illustrated, the plane beveledsurface 25 of the face cutting blade 22 in each knife is arranged in aradial plane across head ll perpendicular to the axis of shaft 112. Theplane beveled surface 24 of the rectangular side cutting blade 21 ofeach knife is arranged in a concial path that is intercepted by theplane of surfaces 25 to form a frustrum of a cone about head 111. It isnot essential that the knives 20 be so oriented, so long as thecorresponding beveled surfaces thereof are mounted in a common radialorientation relative to the axis of shaft l2 and head Ill, with onebeveled surface in a first circular path of movement relative to theaxis of shaft l2, and the second beveled surface in an interceptingpath.

The knife-grinding unit 28 comprises a grinding wheel Sill positioned soas to tangentially engage the beveled surfaces 24, 25 and 26 duringrotation of head If. The line of engagement along surfaces 26 is aradial line in a horizontal plane including the axis of head llll.

The general manner by which the knives 20 are ground by the wheel 30 canbe seen in FIG. 8. Wheel 30 includes a conical grinding surface 31 whichtraverses the respective plane beveled surfaces 24, 25 and which pivotsabout an axis coincident with the corner axis 27 to engage theintermediate curved beveled surfaces 26. The mechanism by which suchmovement is attained by a single-grinding unit 28 is discussed below.

The grinding unit 28 is pivotally mounted to framework by means of anupright post 32 rotatably joumaled by a base bearing 33. Post 32provides a first frame element for grinding unit 28. Offset slightly toone side of the upper end of upright post 32 is a horizontal pivot shaft34 fixed to post 32 by a radially projecting support bracket 35. Shaft34 thereby turns in unison with post 32 about the pivot axis extendingvertically through the center of post 32.

The frame for grinding unit 28 also includes a base 36 pivotally mountedto shaft 34 by depending bearings 37. Bearings 37 support base 36 forpivotal movement about the horizontal axis of pivot shaft 34.

The base 36 of the frame for grinding unit 28 carries an upwardlyextending pedestal 38 which supports the grinding unit 28 at its upperend. The details of the grinding unit 28 will be found below. I

The base 36, which is partially supported by the upright post 32, isalso carried by a pair of arcuately aligned rollers 40 which arerotatably mounted at its underside. The rollers 40 are supported alongthe upper surfaces of three guide plates 41, 42 and 43. The guide plate41, at the center of the guide plate assembly, is stationary and rigidlyfastened to framework 10 by an integral bracket 44. The guide plate 42,shown to the left in FIGS. 1, 4 and 6, is hinged to the abutting end ofplate 41 about a hinged axis designated at 45. The axis 45 isperpendicular to the path of the plane beveled surfaces 25 of knives 20.Likewise, the remaining guide plate 43 is connected to the opposite endof plate 41 by a hinge having an axis 46 which is perpendicular to thepath of the plane beveled surfaces 24 of knives 20.

The plates 42 and 43 are each urged upwardly to positions coplanar withthe center plate 41 by compression springs 47 interposed between theirlower surfaces and the base of framework 10. Normal horizontal alignmentof the plates 41-43 is achieved by abutment of their adjacent edgesabove the respective hinge axes 45, 46.

The angular extent of movement permitted the grinding unit 28 about thevertical axis of post 32 is limited by upstanding stops 48, 50, whichare selectively engaged by the sides of pivot shaft 34. These limits canbe seen in FIGS. 2 and 6, which illustrate the respective positions ofbase 36 on the plates 41, 42 and 43 while the plates are maintained in acommon horizontal orientation.

The base 36 is designed with lateral side edges 51, 52 arrangedimmediately above plates 42, 43 respectively. At the respective limitsof angular movement of base 36 about post 32, the edges 51, 52 willrespectively be aligned at the outer edges of plates 42 and 43. At thisposition, they contact an upstanding ear 53 of a spring-loaded trigger54 which is normally received through a slot 55 at the respective end ofplate 42 or 43. The outward movement of a trigger 54 due to contact ofedge 51 and 52 frees the guide plate for downward pivotal movement aboutaxis 45 or 46 in response to pressure exerted on plates 42 or 43 by therollers 40. Triggers 54 are spring biased to a vertical position so asto be automatically reengaged within the slots 55 upon release of suchpressure.

The design of base 36 is such that the axis of pivot shaft 34 is alignedimmediately above the hinge axis 45 or 46, when pivotal motion aboutpost 32 is arrested by stop 48 or 50, so that the base 36 can then pivotabout the axis of shaft 34 while supported on the released guide plate42 or 43 (see FIG. 7).

Movement of the grinding unit 28 is achieved by a powerdriven crank 56on vertical shaft 57. Shaft 57 is driven by a motor unit shown generallyat 60. This may be an independent motor or a unit driven from a commonpower source such as motor 15. An outwardly extending crank arm 58 isconnected to crank 56 by a universal joint 61, its remaining end beingconnected to an upper plate 62 by a similar universal joint.

The rotational movement of crank 56 is transmitted to the pedestal 38and its supporting frame through crank arm 58. It results in pivotalmovement of the frame base 36 between the limits defined by stop 48, 50.Following release of triggers 54 and arrest of frame movement about post32, crank 56 causes pivotal movement of the grinding unit about thehorizontal axis of shaft 34 while pivot shaft 34 has its axisperpendicular to either the plane beveled surfaces 24 (FIG. 3) or theplane beveled surfaces 25 (FIG. 4).

The grinding wheel 30 is fixed to the axis of a motor 63 which isslidably mounted on plate 62 for endwise movement parallel to the motoraxis. This is accomplished by a shaft 64 journaled on plate 62 at itsends. Shaft 64 has a threaded portion 65 that is threadably engaged in adepending boss on the motor base 66. A handwheel 67 is fixed to theshaft 64 and has peripheral gear teeth which mesh with a pinion 70.Pinion 70 is fixed on a shaft 71 joumaled by bearings 72 depending fromplate 62. Shaft 71 in turn has a ratchet wheel 73 at its end remote frompinion 70. Turning of handwheel 67 can be done by the handle 74 or byturning ratchet wheel 73.

To accomplish automatic turning of ratchet wheel 73, a pawl 75 ispivoted on an upstanding fixed post 76. Post 76 holds the pawl in thepath of ratchet wheel 73. An adjustable stop 77 is threaded into thepost 76 and a leaf spring 78 fixed on the post 76 yieldably holds pawl75 against the stop 77, but allows the pawl 75 to slip over the teeth ofratchet wheel 73 when it is moving away from the post 76.

With this construction, when the pedestal 38 is oscillated to the leftfrom the position shown in FIG. 3, the grinding unit 28 is moved in anarc about the axis of pivot shaft 34 to cause the wheel 30 to traverseeach beveled surface 25 of the face cutting blades 22 moved past it byrotation of head 11. At the finish of each stroke of the grinding unit28, the pawl 75 engages ratchet wheel 73 and turns it a fraction of aturn. This causes pinion 70 to turn the handwheel 67 which will advancethe motor 63 and grinding wheel 30 toward the path of the knives 20. Thegrinding wheel 63 can always be brought to the work or away from it byturning handwheel 67 whenever pawl.

75 is out of engagement with the ratchet wheel 73.

It is believed that the general operation of the apparatus is clear fromthe description above. To grind a set of knives 20, the several knivesare clamped by the individual mounting blocks 17. The grinding unit 28is then adjusted to bring the grinding surface 31 into contact with thebeveled knife surfaces, initial adjustment being accomplished bymanipulation of handwheel 67. The powered motor units 15, 60 are thenactivated to rotate head 1 1 and crank 56 respectively. The head 11rotates the knives past the grinding wheel 30 at a rapid rate (50 rpm.)while the crank 56 is rotated at a relatively slow rate 1 rpm). Themotor 63 for grinding wheel 30 rotates the grinding wheel at a high rateof speed common in grinding applications.

As is evident from the drawings, the grinding unit 28 is pivoted in ahorizontal plane about the axis of post 32 to dress the beveled cornersurface 26 of each knife as schematically shown in FIG. 8. At thecompletion of each pass of the grinding surface 31 across the comersurface 26, such pivotal movement is arrested by engagement of shaft 34by one of the stationary stops 48, 50. Simultaneously, with suchengagement the edge 51 or 52 of base 36 will release the correspondingtrigger 54 to permit the plate 42 or 43 to pivot about its hinge withrespect to the center plate 41. Such pivotal movement will beaccomplished due to continued movement imparted to the grinding unit 28by the crank arm 58, thereby overcoming the upward pressure of springs47. The angular movement of the grinding unit 28 about the axis of pivotshaft 34 continues until the grinding surface 31 traverses the fullwidth of the straight beveled surface at the respective side of theknives 20. The successive pattern of pivotal movement of grinding unit28 about pivot shaft 34 and upright post 32 proceeds in a repetitivefashion from one end of the beveled surfaces to the other to accomplishcomplete grinding of the knife-beveled surfaces by the single-grindingunit: Advancement of the grinding wheel 30 toward the work isautomatically accomplished at the conclusion of each cycle by automaticengagement of pawl 'l'fi as discussed above. The operation of theapparatus is continued until the desired degree of grinding has beenaccomplished, at which time each knife 20 will be ground to an identicalextent so as to form a matched set of knives suitable for chippingpurposes.

When desired, the automatic advancement of the grinding unit 2% can beovercome by turning of handwheel 67. In some instances it might bedesirable to cut steps along the corner bevel of the knives, and thiscan be readily accomplished by manually positioning and setting thegrinding unit as it traverses the corners of knives 2ft.

Obviously, the unit illustrated has been designed specifically forgrinding of a particular knife design. Modification of the apparatus toaccommodate differing knife lengths or blade angles is readilyaccomplished by changing the pivotal axis positions on the grinding unitor by modifying the stroke of the powered crank assembly.

Various modifications might be made in this structure without deviatingfrom the basicconcepts discussed above and the general relationship ofthe elements described in detail herein. Therefore, only the followingclaims are set out as limiting definitions of the disclosed invention.

Having thus described my invention, I claim:

1. In an apparatus for grinding bent chipping knives of the typecomprising a cutting blade having a plane beveled surface terminatingalong a curved beveled surface:

knife-mounting means for releasably fixing a plurality of said knives atpositions located radially outward from a central rotational axis withthe respective knife beveled surfaces exposed and facing outwardly;

power means operatively connected to said knife-mounting means forrotating said knife-mounting means about said rotational axis to therebymove the beveled surfaces of said knives about circular paths centeredabout said rotational axis;

knife-grinding means including a grinding surface tangential to therotational paths of the beveled surfaces of knives on saidknife-mounting means;

said knife-grinding means comprising means for pivoting the grindingsurface along a curved path tangential to the path of the curved beveledsurfaces of said knives about said rotational axis;

said knife-grinding means further comprising means for selectivelyarresting the pivotal movement of the grinding surface about said firstaxis and subsequently reciprocating the grinding surface in a pathtangential to the path of the plane beveled surfaces of said knivesabout said rotational axis.

2. In an apparatus for grinding bent chipping knives of the typecomprising a side cutting blade having a first plane beveled surface, aface cutting blade having a second plane beveled surface, and a curvedbeveled surface joining the respective first and second plane beveledsurfaces:

knife-mounting means for releasably fixing a plurality of said knivesradially outward from a rotational axis with the respective beveledsurfaces thereof exposed and facing outwardly in an arrangement balancedabout said rotational axis;

power means operatively connected to said knife-mounting means forrotating said knife-mounting means about said rotational axis to therebymove the beveled surfaces of said knives about circular paths centeredabout said rotational axis;

knife-grinding means including a grinding surface located tangential tothe rotational path of the beveled surfaces of knives on saidknife-mounting means;

said knife-grinding means comprising means for pivoting the grindingsurface along a curved path tangential to the path of the curved beveledsurfaces of said knives about said rotational axis;

said knife-grinding means further comprising means for selectivelyarresting the pivotal movement of the grinding surface about said firstaxis and subsequently reciprocating the grinding surface in a pathtangential to the path of the plane beveled surfaces of said knivesabout said rota tional axis.

3. in an apparatus for grinding bent chipping knives of the typecomprising a side cutting blade having a first plane beveled surface, aface cutting blade having a second plane beveled surface, and a curvedbeveled surface joining the respective first and second plane beveledsurfaces:

knife mounting means for releasably fixing a plurality of said knivesradially outward from a rotational axis with the respective beveledsurfaces thereof exposed and facing outwardly in an arrangement balancedabout said rotational axis;

power means operatively connected to said knife-mounting means forrotating said knife-mounting means about said rotational axis to therebymove the beveled surfaces of said knives about circular paths centeredabout said rotational axis;

a stationary framework fixed relative to the rotational axis of saidknife-mounting means;

knife-grinding means including a grinding surface for tangentiallyengaging the beveled knife surfaces;

a first frame member pivotally mounted to said framework about a firstaxis;

a second frame member supporting said knife-grinding means and pivotallymounted to said first frame member about a second axis perpendicular tosaid first axis;

and means on said framework operatively connected to said knife-grindingmeans for alternately pivoting said second frame member about saidsecond axis while arresting pivotal movement thereof about said firstaxis to thereby traverse the respective rotational paths of said planebeveled surfaces of the knives about said rotational axis, or to pivotsaid first frame member about said first axis while arresting pivotalmovement of said second frame member about said second axis to therebytraverse the rotational path of said curved beveled surfaces about saidrotational axis.

l. In an apparatus for grinding bent chipping knives of the typecomprising a side cutting blade having a first plane beveled surface, aface cutting blade having a plane beveled surface, and a curved beveledsurface joining the respective plane beveled surfaces of said blades andcentered about a corner axis between the blades:

a stationary supporting framework;

knife-mounting means on said framework for releasably fixing a pluralityof said knives radially outward from a stationary horizontal rotationalaxis on said framework, the respective plane and curved beveled surfacesof the knives being exposed and facing outwardly in an arrangementbalanced about said horizontal rotational axis;

means on said framework operatively connected to said knife mountingmeans for rotating said mounting means about said horizontal rotationalaxis to thereby move said knife-beveled surfaces about circular pathscentered about said horizontal rotational axis;

knife-grinding means including a grinding surface for tan gentiallyengaging the beveled knife surfaces, said knife grinding meanscomprising:

a post centered on said framework about a vertical axis coincident withthe knife corner axis in a horizontal plane containing said horizontalrotational axis;

a frame member mounted to said post about a second axis perpendicular tosaid vertical axis;

a powered grinder mounted to said frame member about said second axisincluding a grinding surface positioned at a height with respect to saidframework so as to engage the curved beveled surfaces of the knivesalong said said knives;

and yieldable guide means on said framework in the path of said framemember about said vertical axis for permitting angular motion of saidframe member relative to said post about said second axis in response tosaid powered means to thereby pass said grinding surface along the pathof the respective plane beveled surfaces following engagement of saidframe member by said motion limiting means

1. In an apparatus for grinding bent chipping knives of the typecomprising a cutting blade having a plane beveled surface terminatingalong a curved beveled surface: knife-mounting means for releasablyfixing a plurality of said knives at positions located radially outwardfrom a central rotational axis with the respective knife beveledsurfaces exposed and facing outwardly; power means operatively connectedto said knife-mounting means for rotating said knife-mounting meansabout said rotational axis to thereby move the beveled surfaces of saidknives about circular paths centered about said rotational axis;knife-grinding means including a grinding surface tangential to therotational paths of the beveled surfaces of knives on saidknife-mounting means; said knife-grinding meAns comprising means forpivoting the grinding surface along a curved path tangential to the pathof the curved beveled surfaces of said knives about said rotationalaxis; said knife-grinding means further comprising means for selectivelyarresting the pivotal movement of the grinding surface about said firstaxis and subsequently reciprocating the grinding surface in a pathtangential to the path of the plane beveled surfaces of said knivesabout said rotational axis.
 2. In an apparatus for grinding bentchipping knives of the type comprising a side cutting blade having afirst plane beveled surface, a face cutting blade having a second planebeveled surface, and a curved beveled surface joining the respectivefirst and second plane beveled surfaces: knife-mounting means forreleasably fixing a plurality of said knives radially outward from arotational axis with the respective beveled surfaces thereof exposed andfacing outwardly in an arrangement balanced about said rotational axis;power means operatively connected to said knife-mounting means forrotating said knife-mounting means about said rotational axis to therebymove the beveled surfaces of said knives about circular paths centeredabout said rotational axis; knife-grinding means including a grindingsurface located tangential to the rotational path of the beveledsurfaces of knives on said knife-mounting means; said knife-grindingmeans comprising means for pivoting the grinding surface along a curvedpath tangential to the path of the curved beveled surfaces of saidknives about said rotational axis; said knife-grinding means furthercomprising means for selectively arresting the pivotal movement of thegrinding surface about said first axis and subsequently reciprocatingthe grinding surface in a path tangential to the path of the planebeveled surfaces of said knives about said rotational axis.
 3. In anapparatus for grinding bent chipping knives of the type comprising aside cutting blade having a first plane beveled surface, a face cuttingblade having a second plane beveled surface, and a curved beveledsurface joining the respective first and second plane beveled surfaces:knife mounting means for releasably fixing a plurality of said knivesradially outward from a rotational axis with the respective beveledsurfaces thereof exposed and facing outwardly in an arrangement balancedabout said rotational axis; power means operatively connected to saidknife-mounting means for rotating said knife-mounting means about saidrotational axis to thereby move the beveled surfaces of said knivesabout circular paths centered about said rotational axis; a stationaryframework fixed relative to the rotational axis of said knife-mountingmeans; knife-grinding means including a grinding surface fortangentially engaging the beveled knife surfaces; a first frame memberpivotally mounted to said framework about a first axis; a second framemember supporting said knife-grinding means and pivotally mounted tosaid first frame member about a second axis perpendicular to said firstaxis; and means on said framework operatively connected to saidknife-grinding means for alternately pivoting said second frame memberabout said second axis while arresting pivotal movement thereof aboutsaid first axis to thereby traverse the respective rotational paths ofsaid plane beveled surfaces of the knives about said rotational axis, orto pivot said first frame member about said first axis while arrestingpivotal movement of said second frame member about said second axis tothereby traverse the rotational path of said curved beveled surfacesabout said rotational axis.
 4. In an apparatus for grinding bentchipping knives of the type comprising a side cutting blade having afirst plane beveled surface, a face cutting blade having a plane beveledsurface, and a curved beveled surface joining the respective planebeveled surfaces of said blades and centered about a corner axIs betweenthe blades: a stationary supporting framework; knife-mounting means onsaid framework for releasably fixing a plurality of said knives radiallyoutward from a stationary horizontal rotational axis on said framework,the respective plane and curved beveled surfaces of the knives beingexposed and facing outwardly in an arrangement balanced about saidhorizontal rotational axis; means on said framework operativelyconnected to said knife mounting means for rotating said mounting meansabout said horizontal rotational axis to thereby move said knife-beveledsurfaces about circular paths centered about said horizontal rotationalaxis; knife-grinding means including a grinding surface for tangentiallyengaging the beveled knife surfaces, said knife-grinding meanscomprising: a post centered on said framework about a vertical axiscoincident with the knife corner axis in a horizontal plane containingsaid horizontal rotational axis; a frame member mounted to said postabout a second axis perpendicular to said vertical axis; a poweredgrinder mounted to said frame member about said second axis including agrinding surface positioned at a height with respect to said frameworkso as to engage the curved beveled surfaces of the knives along saidhorizontal plane containing said horizontal rotational axis; poweredmeans on said framework for reversibly moving said frame member aboutsaid axes; motion limiting means on said framework in the path ofmovement of said frame member about said vertical axis for selectiveengagement by said frame member at angular limits of movement thereofrelative to said vertical axis corresponding to a complete pass of saidgrinding surface across the path of the curved beveled surfaces of saidknives; and yieldable guide means on said framework in the path of saidframe member about said vertical axis for permitting angular motion ofsaid frame member relative to said post about said second axis inresponse to said powered means to thereby pass said grinding surfacealong the path of the respective plane beveled surfaces followingengagement of said frame member by said motion limiting means.